Pulse coincidence indicator



March 1954 B. HAVENS EIAL 2,671,182

PULSE COINCIDENCE INDICATOR Filed 001;. 3, 1945 T0 CATHODE INTENSIFIE GRID v TO VERTICAL VIDEO TARGET ECHO INVENTOR. BYRON L. HAVENS ROBERTMWALKER 2| y IOIOI IIIIIGI. TRACKING 42 4M Q wu,

PIP

ATTORNEY Patented Mar. 2, 1954 "U IT-so srss ears PULSE COINCIDENCE INDICATOR Byron L. Havens, Cambridge, and Robert M. Walker, Belmont, Mass, assignors, by .mesnc assignments, to the United States of America as represented by the Secretary of War Application OctoberB, 1945, Serial No. 621L133 with afsel'ected target echo. Such a pip ifprop erlymaintained in. coincidence maybe used for automatically releasing bombs or otherwise as maybe desired.

It is an object of the present invention, therefore, to provide a method for indicating the coincident. occurrence of two voltage pips.

It is a, further object of the present invention to provide an improved device for indicating the coincident occurrence of two voltage pips.

Fig. I. illustrates schematically a circuit arrangement and cathode .ray indicator resentationjust before the, coincident occurrence of two pulses or pips; and

fiFig'. 2 illustrates the indicator presentation during coincident occurrence.

jltxuis assumed herein that a "13 type scope presentation is used. In a B type presentation,

as is wellknownin the art, the azimuth of targets is givenjby a right or left coordinate and range by 'a' vertical coordinate.

The timer 141 may synchronize the transmitted pulse with the beginning of the vertical or range sweep generated at 40 and applied to the scope at"3'.1, the'pulse repetition rate being the same as the "sweep repetition rate, so that range is indicated by the vertical coordinate of the scope. The-return, echo or video signal is applied by wayfor' input terminal 38 to an intensifier grid orc'athode ofthe cathode ray tube, thereby causmg the indication .I3.

The horizontal sweep or deflection voltage, which 'may be 'alsubstantially sinusoidal signal,

maybe applied to the horizontal deflection input terminal 36. ,The'horizontal sweep frequency is considerablyflower,preferably many times, than the vertical sweep frequency. A tracking pip, synchronized with the beginning of the vertical sweep, may begenerated at 42, having a repetition rate corresponding to the sweep repetition rate-and a time or range interval controlled in. anyconvenient manner well known to the art as by control 43, and may be applied by way of terminal 39' toan'intensifier grid of the cathode. ray time.

As the sinusoidal signal on horizontal deflection control terminals 35 causes the vertical beam sweep to move horizontally back-and'forth across the face of the tube, the beam traces aseries of substantially parallel vertical lines. Thetrackihg pip causes the periodic intensification of-the beam at a corresponding point in each line, hence forming on the tube-screen the luminescenthori-- zontal line 12.

For an example-of a. circuitiorthe generation of the tracking pip as well as a system inwhich the present inventiommay be utilized referenceis had to the copending-applicationof.ByronL.

Havens and John J. Lentz, icr-Electricalsystem, SerialNo. 626,134, filed- October 3, 1945. :Inthis system, the horizontal deflection voltage; periodically varies with the horizontal scanning of the antenna, so that the horizontal coordinate of the tube screen indicates azimuth.

Fig. 2 illustrates the indicator presentation.

when coincidence occurs. It will be noted that the normally straight line formed bythe tracking pip in Fig. l is now distorted at a position corresponding in azimuth to. that of the'target. This conditionis illustrated by line It with its distorted portion 15. This efiect may be accomplished by any circuit cap-able of causing the tracking pip to. occur ata diiierent point on they indicator face It. .Oneexpedient which might be used would be to cause the tracking pip to be delayed, or to delay its time of generation, by an amount proportional .to the amplitude of the return echo pip. Another expedient would be to change the starting level, i. e., the point on the facet I .at whichv range sweep starts, thus shifting all indications at the azimuth of the target;

echo pip. It will be realized by those skilled in the art that other means may be employed producing the desired, distortion of the tracking pip line. I2 .to-indicate coincidence of tracking and target. echo pipe, and, therefore, the invention herein disclosed is not to be construed as being limited to the specific circuits shown herein.

Referring to Fig. l of the-drawing, there is shown a circuit capable of accomplishing the. desired coincidence indication by shifting the starting level of. the range sweep. Besides being connected to the indicator, the tracking pip is coupled through a transformer 21- to tubes 22 and 23, which ar preferably of the triode-type. The tubes 22 andtil are so connected to each other that the plate of tube .22 is connected to the cathode of tube 23, and so that the. cathode of tube 22 is connected to the plate of tube 23. The grids of the tubes 22 andjs are. connected 3 together and connected through a capacitor 22 to one terminal of the secondary winding of transformer 2i. A resistor 25 is connected from the grid to the cathode of tube 23 which is also connected to the remaining terminal of the secondary winding transformer 2i. Besides being connected. to the indicator, the target echo pip is also connected to the cathode of tube 23. The input terminal for this pip is labeled video. A capacitor 26 is connected from the cathode of tube 22 to ground. The cathode of tube 22 is also connected through an isolating resistor 2"! to one control grid 28 of a push-pull amplifier, denoted generally by 3|. The push-pull amplifier comprises tubes 32 and 33 having a common unbypassed cathode resistor 34 for cathode coupling.

1. In pulse coincidence indicator apparatus of the character disclosed, in combination, cathode ray tube indicator means including a beam,

screen, and intensifier means, said cathode ray indicator means having first and second sweep generator means operatively connected thereto, tracking pulse generator means for periodically generating a tracking pulse, said last mentioned means synchronized with said first sweep gen- As aforementioned, a sawtooth voltage to provide range sweep on the indicator is applied to the remaining control grid 25 of amplifier 31. The resultant amplified sawtooth sweep voltage is taken in push-pull from the plates of tubes 32 and 33 and applied to the indicator of the radio object-locating equipment. It will be obvious to those skilled in the art that the starting level of the range sweep on the indicator is dependent upon'the potential of grid 28. Therefore, if the potential of grid 28 is made to vary in accordancewith the amplitude of the target echo pip, the desired coincidence indication will result.

' It-wi1l now be shown that the potential across capacitor 26 and at grid 28 varies in accordance with the amplitude of the target echo pip. It is first assumed that no potential exists across capacitor 24. The tracking pip is impressed across the primary winding of transformer 25, and a voltage pulse appears across the secondary winding; The-magnitude of this pulse may be as high as 100 volts. The polarity of this pulse is such that the grid of tube 23 tries to go positive with resulting grid current flow which will charge capacitor 24 with a polarity as shown. While the pulse is applied, tube 22 is in such a state as to conduct if the potential on the video terminal is higher than-the potential across capacitor 26.

Further, if the potential on the video terminal is lower than the potential on capacitor 26, tube 23 will conduct. It will thus be seen then that the potential across capacitor 28 will, during the time of application of the tracking pip, change in such a manner as to become the same as the potential at the video terminal. After the occurrence ofthe tracking pip, the potential across the secondary winding of transformer 2| becomes zero, but now the capacitor 2%, which must discharge slowly through resistor 25 so biases tubes 22 and 23 that they are rendered nonconducting, and the potential across capacitor 26 remains at the value which it attained during the time of I occurrence of the tracking pip. The above action will occur with each incoming tracking pip, and the potential on grid 28 will vary in accordance with the amplitude of the target echo pip. It is #'to be noted that the potential across capacitor 26 cannot charge from zero unless the tracking pip andthe target echo pip occur at the same time,

and, therefore, shifting of the starting level of the range sweep is an accurate indication of coincidence between tracking and echo pips.

While there has been described what is at present considered the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention.

What is claimed is:

erator means and operatively connected to said intensifier, means, whereby th tracking pulse periodically actuates said intensifier means to intensity modulate said beam thereby forming a trace on said cathode ray tube said intensifier means being adapted to have a target echo pulse also applied thereto, said target echo pulse intensity modulating said sweep thereby forming a target on said screen and sweep modulator means operatively connected tqsaid first sweep generator means and having said tracking pulse and target echo pulseapplied thereto for supplying a modulator output, said first sweep generator means being adapted to b modulated by said output to instantaneously increase the sweep amplitude thereby to indicate on said screen substantial concurrence of the tracking pulse and target echo pulse.

2. In apparatus of the character disclosed'forv indicating the coincidence of two pulses, in combination, cathode ray oscilloscope means having" for periodically intensifying the beam thereof in' accordance with a pulsed tracking signal, said,

pulsed tracking signal being in substantial syn chronism with the first sweep, second intensifier. means connected to said oscilloscope for periodie 1 cally intensifying the beam thereoffin accordance," with a second pulsed signal, and means energized by said tracking signal and second pulsed signal and operatively connected to said electron discharge tube for alteringthe potential 'on saidgr'id thereby to momentarilyincrease the sweep volt age and indicate substantial concurrence on the screen of the pulse positions.

3. In apparatus of the character disclosed for" indicating the coincidence between two puisegin combination, a cathode ray oscilloscope havinga} screen and having first and second; deflecting means for deflecting the beam in first and second substantially mutually perpendicular directions, said oscilloscope also having first and second. beam intensifier elements, generator means con'a, nected to said oscilloscopefor' applying a pulsed f linear sweep voltage tosaid first defiectingr'neans,

means connected tosaid oscilloscope for apply ing an additional periodically varying sweep voltage to said second deflecting means, means connected to said oscilloscope for applying fa. first pulsed signal voltagehaving the same repetition frequency as the linear sweep voltage to said first intensifier element infsynchronization with'said 1 linear'sweep voltage thereby to form a lum'inascent spot indication at a predetermined place" on said screen corresponding'to the time rela-i:

tlonship between the sweep voltage and said pulsed signal: voltage, means connected to said.

pulsedsweep voltage thereby to form a second indication on said-screen, and sweep modulator means'having said pulsed tracking voltage and said-pulsed signal voltage applied thereto and connected to said'linear sweep generator means for causing-the sweep voltage to be momentarily increased when the pulsed tracking voltage and pulsed signal voltage are in substantial time coinc'idence thereby to cause the'two indications on the screento blend-into a markedly unified 'indication;

' -14, .In-apparatus of the character disclosed for indicating the coincidence between two pulses, in combination, a cathode ray oscilloscope having ascreenand having first and second deflecting means for deflecting the beam in first and second substantially mutually perpendicular planes, said oscilloscope having first and second beam intensifier-elements,-generator means connected to said oscilloscope forapplying a pulsed linear sweep voltage'to said first deflecting means, said generator means-comprising a saw tooth signal generator; and a signal amplifier including a pair of electron discharge tubes each having a grid, cathode, .'and anode, the saw tooth signal being appZlied'to'the' gridof one oi said tubes, said cathbdes being operatively connected together, said-,anodesflbeing operatively connected to said firstdefiecting means, mean connected to said oscilloscope for applying an additional periodica'll'y varying sweep voltage to said second defleeting means, means connected to said oscillosco'pe for applying a first pulsed signal voltage having thesame repetition frequency as the linearysweep voltage to said first intensifier ele ment in synchronization with said linear sweep voltage thereby to form a luminescent spot indication at a predetermined place on said screen corresponding to the time relationship between the sweep voltage and said pulsed signal voltage, means connected to said second intensifier element for applying a pulsed tracking voltage thereto having a repetition frequency corresponding to the frequency of the pulsed sweep voltage thereby to form a second indication on said screen, and bias generating means having said pulsed tracking voltage and said pulsed signal voltage applied thereto and connected to the grid of the other of said pair of electron discharge tubes for causing the sweep voltage to be momentarily increased when the pulsed tracking voltage and pulsed signal voltage are in substantial time coincidence thereby to cause the two indications on the screen to blend into a markedly unified indication.

5. Apparatus according to claim 4 wherein said I bias generating means comprises an additional j pair of electron discharge tubes, each tube of said 'additional pair having a cathode, grid, and anode,

said last named grids being connected together, an input transformer having a primary and secondary, said primary being energized by said pulsed tracking signal, a capacitor, said secondary having one end thereof connected to the anode of one of said last named pair of tubes and the cathode of the other of said last named pair of tubes, said end having said pulsed signal voltage applied thereto, the other end of said secondary being connected by way of said capacit'or to said last named grids-2a resistor connected between said last ,named grids and sai'cl'iast named cathode and anode, and resistance-capacitance network-means connecting; the remaining anode and remaining cathode of said :last named pair of tubes to the first named pair of tubes, said bias generating means providing a bias to said last named grim .6. vA pulse coincidence indicatQroomprising-a cathode ray tubehaving a beam, beam intensifier:

means, and a plurality of-sweep generator means, tracking pip generator means for periodically generating a tracking pip operativelyzconnectedz to one of said sweep generator means andlopera tive :in timed relation :to said sweep generator meam, said tracking pip "generator means being connected to said lbeanr intensifier means so that the periodic occurrence of the generated tracking pip will intensity modulate the sweep at a predetermined portion-thereof and thereby form a tracking pip trace, sweep generator modulation means, said tracking :pip generator meansbeing operatively connected to said sweep generatormodulation means, a target echo receiving means; said target echo receiving means also being ope eratively connected to said sweep generator modulation means and to said beam intensifier:

means, said sweep generator modulation means being operatively connected to said one 'zsweep generator means whereby the sweep signal generated by the said one sweep generatorinsanedismodulated in accordance with the intelligencereceived from the tracking pip generator means and the target echo receiving means to cause a I portion of the tracking pip trace to become distorted to thereby signify the pulse coincidence of the target echo and the tracking pip.

7.. A pulse coincidence indicator comprising av cathode ray tube having a beam, screen,-a -p1-u-- rality of sweep generator means, and beam intensifier means, a pip generator connected by means of operative connections to one of said sweep generators and to said beam intensifier means and operative in timed relation relative to said sweep generator means, whereby periodic pip generator by said pip generator periodically causes an intensification of said beam to thereby form a trace on said screen, a signal pulse, said signal pulse also being applied to said beam intensification means for periodically intensifying said beam means and thereby forming a signal response on said screen, said signal pulse also being connected by means of operative connections to said one sweep generator means, said operative connections between said signal pulse and sweep generator means and between said pip generator and said sweep generator means comprising means for modulating said sweep formed by said sweep generator means to thereby cause said trace to be distortecl whenever said tracking pip and said signal pulse are simultaneously applied to said means for modulating said sweep.

8. A pulse coincidence indicator comprising a cathode ray tube having a beam, a screen, first and second sweep generating means, and beam intensifying means, the first of said sweep generating mean causing said beam to linearly traverse the screen, the second of said sweep generator means operative in timed relationship to said first sweep generating means and thereby causing said first sweep generating means to generate a series of parallel lines on the screen, tracking pip generator means connected to said beam intensifier means, operative connection grid :of the other of ,said' means connecting said tracking pip generator means to said first swee generating means, said.

' being capable of applying said tracking pip and target echo to said first sweep generating means only when they are simultaneously impressed on said operative connection means to cause the trace which is formed by said tracking pip to become distorted thereb indicating coincidence of the tracking pip and the target echo.

, 9. A pulse coincidence indicator comprising a oathoderay tube having a beam, a screen, first and second sweep generating means, and beam intensifier means, the first of said sweep generating means causing said beam to traverse the s'creen,the second of said sweep generating means operative in timed'relationship to said first sweep generating means to cause said first sweep generating means to generate a series of substantially equidistantly spaced lines on said screen. a tracking pip generator means for generating a tracking pip pulse, said tracking pip generator means being connected to said beam intensifier means andgenerating said pulse in timed relationship to said first sweep generator means wherebythrough the energization of said beam intensification means by said tracking pip generator pulse, a predetermined portion of each of said. lines is intensified and the series of intensificationsthus formed combine to form a trace on said screen, operative connection means connecting said tracking pip generating means to said first sweep generating means, a second pulse, said operative connection means also connecting said 8 second pulse to said first sweep generator means, said operative connection means being operable onl when said tracking pip pulse andsaid second ulse are simultaneously applied thereto whereby the trace on the screen is caused to become distorted to indicate coincidence between the tracking pip pulse and the second pulse.

10. A pulse coincidence indicator as set forth in claim 9 wherein said operative connection means comprise first and second space discharge devices each having a cathode, plate, and grid, said devices being connected so that the plate of the first of said devices is connected to the cathode of the second and the plate of the sec-- ond is connected to the cathode of the first, and the grids of said devices are connected together, the tracking pip pulse being applied to said grids and the second pulse being applied to the oathode of said first discharge device, and the oathode of the second discharge device being con-' nected to the output of the first sweep generator so as to modify the output of said first sweep generator.

BYRON L. HAVENS. ROBERT M. WALKER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,355,363 Christaldi Aug. 8, 1944 2,375,709 Thompson May 8, 1945, 2,404,527 Potapenko July 23, 1946 2,425,330 Kenyon Aug. 12, 1947, 2,448,041 Marchand Aug. 31, 1948 2,453,711 Isbister et a1. Nov. 16, 1948 2,465,368 Frink Mar. 29, 1949 2,480,837 Busignies Sept. 6, 1949 2,492,700 Jeanne Dec. 27,1949

FOREIGN PATENTS Number Country Date a 552,072 Great Britain Mar. 22, 1943' 

